High intensity light source



p 6, 1969 N. J. RIVERA 3,467,823

HIGH INTENS-ITY LIGHT SOURCE Filed March 3, 1957 I NVEN TOR.

Q 2 7 ,2 6 {Kzflfla use-EVER "add/4am I Jag/9 United States Patent 3,467,823 HIGH INTENSITY LIGHT SOURCE Nazario J. Rivera, Buenos Aires, Argentina, assignor to Emil Velazco, Buenos Aires, Argentina Filed Mar. 3, 1967, Ser. No. 620,432 Claims priority, applicatgiozrbgargentina, Sept. 2, 1966,

Int. Cl. Fzis 1/12, 9/00 US. Cl. 240-81 7 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to high intensity lamps. More specifically, this invention concerns high intensity low voltage lamps suitable for use as reading lamps.

High intensity lamps are well known. These lamps, however, are of the on-off control type. That is to say, a switch is provided which enables the lamp to be turned on or off but does not enable the intensity of the lamp to be varied. In view of the use of these types of lamps for reading lights, it would be advantageous to have such a variable intensity control, in order to adapt the lamp to use in accordance with various circumstances such as distance from the reading material, the general background light, and the nature of the material being read.

The present invention suggests a high intensity lamp with a simple and inexpensive control means which is effective to vary the intensity of the lamp in a smooth and continuous manner. According to the instant invention, a voltage step-down transformer is provided having a secondary coil which has a portion thereof uninsulated. A wiper contact is provided and is in electrical contact with this uninsulated portion of the secondary Winding. The bulb of the lamp is connected to one end of the secondary winding and the wiper contact, whereby, as the wiper is moved across the secondary, a variable voltage dependent upon the relative position of the wiper, is supplied to the lamp.

The present invention may be more fully understood by reference to the following detailed description along with the drawings in which:

FIGURE 1 is a perspective view of a lamp constructed in accordance with the present invention.

FIGURE 2 is a cut-away view of another embodiment of the invention showing the control means used therein.

FIGURE 3 is a schematic illustration showing the relative dimensions of the wire used in the transformer and the wiper contact.

FIGURE 4 is a schematic wiring diagram of the circuit used in the control system of FIGURE 2.

In FIGURE 1, there is shown a perspective view of a high intensity lamp constructed in accordance with the present invention. Housing 1 contains the control mechanism (to be described hereinafter) for varying the voltage applied to a lamp 2. This lamp may be any suitable incandescent bulb capable of generating high intensity light. In accordance with the instant invention, the lamp is a small incandescent bulb responsive to a voltage between 0 and volts, to produce a high intensity illumination. An articulating arm 3 of any suitable construction is fixedly mounted on the housing at 4 and has a shade ice or reflector 5 mounted at its free end. Suitable socket means (not shown) are also provided at the free end of the arm for receiving the bulb. The articulating arm is hollow and provides a conduit for the wires (not shown) connecting the voltage from the control mechanism to the lamp. Dial 6 is rotatably mounted in the upper surface 7 of housing 1. Scale 8 may be provided and may be calibrated in terms of voltage, brightness or any other suitable parameter. A plug 10 and cord 11 are provided to connect the lamp to a conventional AC source.

FIGURE 2 shows a cut-away view of the lamp similar to that shown in FIGURE 1. The housing 20 is cut away to show the control mechanism which comprises a transformer 21 having a core 22 and a secondary winding 30. The primary winding of the transformer is not shown, as it is wound on a core beneath the secondary winding. The ends of the primary winding are connected to the terminals 24 and 25 which are in turn connected to a plug 26 via cord 27. The plug is attached to be inserted into any suitable AC source such as the volt receptacle found in a house.

Suitable insulating members 28 and 29 are interposed between the ends of the secondary windings and the core. A portion of the secondary winding is uninsulated as shown at 30. This may be accomplished by filing down the windings to thereby remove the insulation of fabricating the secondary in such a way that a portion thereof does not receive insulation such as by employing masking techniques. A wiper contact 31 of suitable electrically conductive material has a contact portion 32 at one end thereof which is in electrical contact with the uninsulated portion of the secondary, the other end of this wiper connects to a shaft 33 which is rotatably mounted in bracket 34 which may be fixedly attached to the transformer in any suitable manner. The transformer itself is fixedly secured to the housing to prevent relative movement thereof. The shaft 33 passes through the housing and is embedded in a dial 35. In this manner, rotation of the dial causes the contact portion 32 to move transversely across the uninsulated portion of the secondary as illus trated by arrows 39.

The wires of the secondary winding have been chosen to be 1 and /2 mil. wide and the contact portion 32 of wiper 33 is 2 mil. wide, for example. In other words, the

wiper contact 32 is to be always less than the width of two secondary coil wires 46 (FIGURE 3) and more than the width of one such wire. In this manner, as can be seen from FIGURE 3, the contact is resting at all times on at least one of wires 46 and therefore, there is never an interruption of current flowing to the lamp as a contact is moved across the uninsulated portion of the secondary. It is to be understood that the particular sizes described herein are merely exemplary and may be of any suitable dimensions which enable the contact to always rest on at least one and no more than two wires of the secondary.

In the modification shown in FIGURE 2, a hollow flexible arm 40 having a rigid portion 41 and a flexible section 42 is attached to the housing and communicates with the interior thereof. At the free end of the flexible arm is mounted a shade or reflector 43. A socket for receiving the light bulb (not shown) is suitably aflixed to the end of the flexible arm. Electrical conductors 44 and 45 extend through the flexible arm and are connected to the socket. Electrical conductor 44 is also connected to one end of the secondary via a switch 55 (FIGURE 4) and the conductor 45 is connected to the wiper contact through bracket 34 and shaft 33. In this manner the output voltage across one end of the primary and wiper contact is connected to the light bulb and a high intensity lamp is provided in which the intensity of the lamp may be varied from zero to a maximum value in a smooth and continuous manner.

It is to be understood that the specific features of the hereinbefore described preferred embodiment of the instant invention have been used merely to more clearly describe this invention and are not intended to limit the scope thereof. Many modifications are contemplated as being within the scope of this invention such as the use of any other suitable transformers having a turns ratio dictated by the particular source of AC voltage available, e.g., 110 or 220 v. AC and the rating of the particular bulb to be used. Furthermore a single secondary winding may be used in place of the split secondary shown having sufiicient turns to provide any desired range of output voltage. The scope of the present invention is therefore to be determined only by reference to claims appended hereto.

An example of a suitable transformer for use in the instant invention is a shell-type transformer having a split secondary as illustrated in FIGURE 4. In the present example chosen, the turns ratio is such that with 110 volts AC applied to the primary, the output across the entire secondary is 7.2 volts AC. The secondary comprises two windings, each having 21 turns. In actual construction only the winding 51 has an insulated portion. The winding 52 is completely insulated and is disposed beneath the Winding 51 on the core.

As can be seen from FIGURE 4 the secondary windings 51 and 52 are connected at one end by lead 53. Primary 54 is adapted to be connected to an AC source of 110 volts. The other ends of the secondary windings 51 and 52 are connected to terminals 56 and 57 respectively of a switch 55 which is of the single pole double throw type having an armature 58. The switch has two positions as shown. The armature is connected to one terminal of lamp 2 and the other terminal of the lamp is connected to the wiper contact.

In operation, when the armature is in position I, only winding 51 is effective to apply voltage to the lamp. Winding 52 is open circuited. As the wiper contact 32 moves from the top of winding 51 to the bottom, the number of effective turns on the winding is increased which thereby increases the voltage applied to the lamp from zero at the upper position of 3.6 volts in the bottom position. If the armature of switch 55 is now moved to position II, secondary 51 is open circuited and secondary 52 is connected in circuit with the lamp and since the secondary windings have an equal number of turns the voltage across the lamp does not change. As the 'wiper contact is now moved upward, an increasing number of turns on winding 51 are connected in series with the winding 52 and voltage across the lamp increases to 7.2 volts when the wiper contact is at the top of winding placing all of the turns in this winding in series with the winding 52.

What is claimed is:

1. A high intensity lamp comprising:

a housing containing a voltage step-down transformer having an insulated primary coil and a secondary coil which is insulated except for a given portion of adjacent turns uninsulated so as to electrically expose the secondary coil,

means connected to the said primary coil and extending beyond said housing, adapted to be connected to a source of voltage,

a movable wiper disposed to be in electrical contact with at least one wire of said secondary coil via its said exposed portion, and

means connected to said wiper and one end of said secondary coil and having means for accommodating an electric bulb, whereby movement of said wiper across said exposed portion of the secondary coil regulates the amount of voltage delivered to said bulb for controlling the amount of light therefrom,

.4 wherein said secondary coil is a split winding having a first coil and a second coil, said second coil being completely insulated and disposed beneath said first coil, said first coil being partially uninsulated, said wiper contact being in contact with said uninsulated part of said first coil and switch means having first and second positions for selectively connecting said first and second coils to said lamp, said switch when in said first position being effective to open circuit said second coil to connect a portion of said first coil defined by the position of said wiper contact in series with said lamp and when in said second position being effective to connect said second coil and a portion of said first coil defined by the position of said wiper contact in series with said lamp.

2. The device claimed in claim 1 wherein said wiper contact is adapted to be moved transversely across said secondary coil, said wiper contact being wider than the diameter of the wire comprising said secondary coil such that said wiper contact rests at all times on at least one turn of said secondary coil.

3. The apparatus as claimed in claim 1 wherein intensity control means are provided comprising:

a rotatable dial member rotatably mounted on said housing and means connecting said dial member to said contact to move transversely across said uninsulated portion of said secondary in response to rotation of said dial.

. A high intensity lamp comprising:

a housing having means for stepping down a source voltage and including first and second serially connected voltage output impedance elements at least one of which has at least a portion that is unin sulated,

a wiper disposed in electric contact with and movable along said uninsulated portion of said one impedance element,

means for accommodating an electric bulb and being connected serially with said wiper, and

switch means serially connected to said bulb accommodating means for alternately connecting the bulb accommodating means to opposite ends of said serially connected impedance elements to cause the voltage delivered to said bulb accommodating means to alternately exclude and include the voltage across the other of said first and second impedance elements.

5. A high intensity lamp as in claim 4 wherein said first and second impedance elements are transformer coils.

6. A high intensity lamp as in claim 5 wherein the one of said coils that contains said uninsulated portion is disposed about the other of said coils which is insulated.

7. A high intensity lamp as in claim 4 wherein said voltage stepping down means includes a transformer having a primary winding and a secondary winding which is split into two coils which are respectively said first and second impedance elements.

References Cited UNITED STATES PATENTS 2,715,197 8/1955 Dubroff et a1. 24081 2,876,320 3/1959 Blaustein 336-149 2,976,477 3/1961 Carpenter 336149 3,315,073 4/1967 Minoru Araki 240-81 NORTON ANSHER, Primary Examiner DAVID S. STALLARD, Assistant Examiner U.S. Cl. X.R. 336-l49; 240123 

